xen: don't print error message in case of missing Xenstore entry

xen: don't print error message in case of missing Xenstore entry

When registering for the Xenstore watch of the node control/sysrq the
handler will be called at once. Don't issue an error message if the
Xenstore node isn't there, as it will be created only when an event
is being triggered.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Orabug: 26841566

(cherry picked from commit 4e93b6481c87ea5afde944a32b4908357ec58992)
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Shannon Nelson <shannon.nelson@oracle.com>